Iowa Tests of Basic Skills (ITBS)

Mathematics

Rating Summary

Classification Accuracyfull bubble
GeneralizabilityModerate High
Reliabilityhalf bubble
Validityfull bubble
Disaggregated Reliability and Validity DataN A
Efficiency
AdministrationGroup
Administration & Scoring Time60 Minutes
Scoring KeyComputer Scored
Benchmarks / NormsYes
Cost Technology, Human Resources, and Accommodations for Special Needs Service and Support Purpose and Other Implementation Information Usage and Reporting

Test booklets are sold in packages of 25 booklets. Each package includes one Directions for Administration.

Students mark their answers using a separate answer document. Answer documents may be centrally scored by the Riverside Scoring Service® or locally scored either by hand or through use of the Riverside Local ScoringPro™ software.

Cost per student for Year 1: $20.26* which includes: directions for administration; interpretive guide for teachers and counselors; interpretive guide for school administrators; test forms; guide to research and development; norms and score conversions booklet; protocol (answer document); and basic scoring service.

Cost per student for subsequent years: $4.67 for the protocol and basic scoring service.

* Per-student pricing assumes 1 of each of the identified manuals for every 25 students. Includes Math and Reading together for this price.

Computer access is required for full use of product services.

Testers will require less than 1 hour of training.

Accommodations: Braille and Large-Print editions are available for students with visual impairments. In addition to these special editions, the standardization of the Iowa Tests of Basic Skills also included students using a wide range of accommodations. Such accommodations included the following: extended time, individual/small group administrations, communication assistance, repeated directions, tests read aloud, answers recorded, transferred answers, and tested off level. Those same accommodations can be used when the tests are administered operationally.

Riverside Publishing
3800 Golf Road, Suite 100
Rolling Meadows, Illinois 60008
Phone #: 800-323-9540

Web Site: www.riversidepublishing.com

Training manuals are available and should provide all implementation information. Ongoing technical support is available through toll-free telephone support and Riverside Field Staff.

The Iowa Tests of Basic Skills measure the skills, academic growth, and achievement of students from Kindergarten through Grade 8.

Form C reflects the most up-to-date thinking about curriculum as represented in current content standards, curriculum frameworks, and instructional materials. All test materials have been extensively field tested for psychometric soundness and evaluated for fairness to gender, racial, ethnic, and cultural groups. Test content was chosen for its appeal and interest to children in order to provide test takers with an engaging and motivating testing experience.

ITBS Math takes 60 minutes to administer (assumes using only the Reading Comprehension, Math Concepts and Estimation, and Math Problem Solving and Data Interpretation subtests). Tests are centrally scored.

Two alternate forms are available for grade 3, and three alternate forms are available for each grades 4 through 8.

Available scores include: raw; standard; percentile; stanines; normal curve equivalents; equated; lexile; subscale/subtest; composite; and predicted.

The number of questions a student gets right on a test is the student’s raw score. By itself, a raw score has little or no meaning, and so raw scores are usually converted to other types of scores for interpretational purposes, including standard scores. Composite scores are obtained by averaging the developmental standard scores from certain component tests. The average standard score can be converted to a percentile rank, grade equivalent, or other type of score for interpretational purposes.

 

Classification Accuracy

Classification Accuracy in Predicting Proficiency Level on the State Accountability Test


 
3rd grade
n=11,445
4th grade
n=6,738
5th grade
n=11,457
6th grade
n=6,681
7th grade
n=6,868
8th grade
n=11,412
False Positive Rate 0.128 0.065 0.115 0.028 0.065 0.059
False Negative Rate 0.281 0.431 0.273 0.612 0.435 0.458
Sensitivity 0.719 0.569 0.727 0.388 0.565 0.542
Specificity 0.872 0.935 0.885 0.972 0.935 0.941
Positive Predictive Power 0.413 0.757 0.485 0.925 0.761 0.783
Negative Predictive Power 0.961 0.859 0.956 0.643 0.854 0.839
Overall Classification Rate 0.855 0.839 0.865 0.698 0.836 0.828
AUC (ROC) 0.896 0.908 0.912 0.903 0.907 0.907
Base Rate 0.112 0.263 0.129 0.469 0.268 0.283
Cut Point:
Math total without Computation SS
161 176 186 191 197 209
At 90% Sensitivity, Specificity equals 0.746 0.771 0.777 0.725 0.739 0.748
At 80% Sensitivity, Specificity equals 0.824 0.845 0.839 0.834 0.849 0.837
At 70% Sensitivity, Specificity equals 0.827 0.901 0.886 0.894 0.885 0.882

Midwestern Replication

Classification Accuracy in Predicting Proficiency Level on the State Accountability Test


 
3rd grade
n=1,009
4th grade
n=1,048
5th grade
n=1,123
6th grade
n=1,149
7th grade
n=1,035
8th grade
n=1,028
False Positive Rate 0.143 0.127 0.115 0.055 0.034 0.041
False Negative Rate 0.259 0.280 0.382 0.497 0.600 0.592
Sensitivity 0.741 0.720 0.618 0.503 0.400 0.408
Specificity 0.857 0.873 0.885 0.945 0.966 0.959
Positive Predictive Power 0.512 0.616 0.738 0.874 0.910 0.881
Negative Predictive Power 0.942 0.916 0.815 0.715 0.648 0.688
Overall Classification Rate 0.837 0.839 0.793 0.755 0.701 0.726
AUC (ROC) 0.882 0.888 0.849 0.882 0.903 0.886
Base Rate 0.168 0.221 0.345 0.431 0.467 0.424
Cut Point:
Math total without Computation SS
161 176 186 191 197 209
At 90% Sensitivity, Specificity equals 0.685 0.654 0.595 0.667 0.734 0.686
At 80% Sensitivity, Specificity equals 0.800 0.796 0.746 0.789 0.830 0.809
At 70% Sensitivity, Specificity equals 0.866 0.875 0.839 0.862 0.911 0.876

 

Generalizability

Description of study sample:

  • Number of States: One; two other states in replication
  • Size:
    • State 1: 54,601
    • State 2: 6,392
  • Region: Southeastern U.S.; replication in Midwestern U.S.
  • Gender: general education population with an approximate 50-50 gender distribution
  • First language: general education populations; primarily English
  • Language proficiency status: general education populations; primarily proficient in English

Reliability

Type of Reliability Age or Grade n (range) Coefficient SEM Information / Subjects
range median
K-R 20 (alpha) Grade 3 4 0.900 to 0.912 0.907 5.8-6.1 Reliability estimates were derived from the 2000 and 2005 ITBS national standardization samples of approximately 4,000 to 15,000 nationally representative students, and include both Fall and Spring estimates.
K-R 20 (alpha) Grade 4 4 0.903 to 0.918 0.910 6.7-7.0 Reliability estimates were derived from the 2000 and 2005 ITBS national standardization samples of approximately 4,500 to 15,000 nationally representative students, and include both Fall and Spring estimates.
K-R 20
(alpha)
Grade 5 4 0.913 to 0.927 0.920 7.4-7.6 Reliability estimates were derived from the 2000 and 2005 ITBS national standardization samples of approximately 4,000 to 15,000 nationally representative students, and include both Fall and Spring estimates.
K-R 20
(alpha)
Grade 6 4 0.921 to 0.929 0.925 8.1-8.2 Reliability estimates were derived from the 2000 and 2005 ITBS national standardization samples of approximately 5,000 to 15,000 nationally representative students, and include both Fall and Spring estimates.
K-R 20
(alpha)
Grade 7 4 0.925 to 0.935 0.930 8.6-8.7 Reliability estimates were derived from the 2000 and 2005 ITBS national standardization samples of approximately 6,000 to 15,000 nationally representative students, and include both Fall and Spring estimates.
K-R 20
(alpha)
Grade 8 4 0.929 to 0.938 0.933 9.0-9.2 Reliability estimates were derived from the 2000 and 2005 ITBS national standardization samples of approximately 4,000 to 15,000 nationally representative students, and include both Fall and Spring estimates.

 

Validity

Type of Validity Age or Grade Test or Criterion n (range) Coefficient Information / Subjects
range median
Content Grade 3 – Grade 8         Alignment of test with National Council of Teachers of Mathematics (NCTM) Assessment Standards for School Mathematics; Curriculum and Evaluation Standards for Mathematics.
Construct / Content Grade 3 – Grade 8         Fairness review by independent and representative panel, of all Mathematics Test items identified as functioning differently based on gender or ethnicity (African American/Caucasian, Hispanic/Caucasian). A conditional group difference of  0.15 or greater on the proportion correct scale was used as the criterion for review. Of the 589 Mathematics items analyzed, 40 were flagged for review. Items identified by reviewers as problematic were either revised to eliminate objectionable features of eliminated from the final test form.
Construct / Convergent Grade3 State assessment 1,000-11,500 0.76 - 0.81 0.78 Correlation of ITBS Math scores with Math scores of two state (one Southeastern; one Midwestern) end-of-grade assessments.
Construct / Convergent Grade 4 State assessment 1,000-6,700 0.80 - 0.80 0.80
Construct / Convergent Grade 5 State assessment 1,100-11,500 0.76 - 0.83 0.79
Construct / Convergent Grade 6 State assessment 1,100-6,700 0.77 - 0.83 0.80
Construct / Convergent Grade 7 State assessment 1,000-6,900 0.86 - 0.87 0.87
Construct / Convergent Grade 8 State assessment 1,000-11,500 0.84 - 0.85 0.84